title: Beneficial hemodynamic effects of prone positioning in patients with acute respiratory distress syndrome.
abstract: BACKGROUND
  The effects of prone positioning during acute respiratory distress syndrome on all the components of cardiac function have not been investigated under protective ventilation and maximal alveolar recruitment.
  
  
  OBJECTIVE
  To investigate the hemodynamic effects of prone positioning.
  
  
  METHODS
  We included 18 patients with acute respiratory distress syndrome ventilated with protective ventilation and an end-expiratory positive pressure titrated to a plateau pressure of 28-30 cm H2O. Before and within 20 minutes of starting prone positioning, hemodynamic, respiratory, intraabdominal pressure, and echocardiographic data were collected. Before prone positioning, preload reserve was assessed by a passive leg raising test.
  
  
  RESULTS
  In all patients, prone positioning increased the ratio of arterial oxygen partial pressure over inspired oxygen fraction, the intraabdominal pressure, and the right and left cardiac preload. The pulmonary vascular resistance decreased along with the ratio of the right/left ventricular end-diastolic areas suggesting a decrease of the right ventricular afterload. In the nine patients with preload reserve, prone positioning significantly increased cardiac index (3.0 [2.3-3.5] to 3.6 [3.2-4.4] L/min/m(2)). In the remaining patients, cardiac index did not change despite a significant decrease in the pulmonary vascular resistance.
  
  
  CONCLUSIONS
  In patients with acute respiratory distress syndrome under protective ventilation and maximal alveolar recruitment, prone positioning increased the cardiac index only in patients with preload reserve, emphasizing the important role of preload in the hemodynamic effects of prone positioning.
authors.affiliation: 1 Service de Réanimation Médicale and.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Jozwiak
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Teboul
authors.forename: Nadia
authors.initials: N
authors.lastname: Anguel
authors.forename: Romain
authors.initials: R
authors.lastname: Persichini
authors.forename: Serena
authors.initials: S
authors.lastname: Silva
authors.forename: Denis
authors.initials: D
authors.lastname: Chemla
authors.forename: Christian
authors.initials: C
authors.lastname: Richard
authors.forename: Xavier
authors.initials: X
authors.lastname: Monnet
mesh_terms: D000005:Abdomen / Q000503:physiopathology; D000368:Aged; D017548:Echocardiography, Transesophageal; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D056888:Patient Positioning / Q000379:methods*; D011175:Positive-Pressure Respiration; D011312:Pressure; D016684:Prone Position / Q000502:physiology*; D012128:Respiratory Distress Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D012129:Respiratory Function Tests; D016896:Treatment Outcome; D014655:Vascular Resistance